A day after tearing his anterior cruciate ligament (ACL) in practice, the Chargers outside linebacker walked Wednesday. He expressed optimism about the long recovery ahead. On Twitter, he called the situation "one minor setback to a major comeback."

First, surgery awaits.

The 24-year-old is tentatively expected to undergo ACL reconstruction surgery on his left knee next week, a source said. Dr. James Andrews will perform it.

There are recorded cases of an athlete roaring back from such a procedure, defying his timetable. But those cases are extremely rare.

Ingram is expected to miss the 2013 season, the equivalent of a redshirt year, before returning to the field in 2014 at or near full strength.

For Andrews, this will be the second member of the Chargers' 2012 draft class on whom he's performed a major knee operation. Safety Brandon Taylor, a third-round pick, tore his ACL in December and had surgery in January.

Ingram was the Chargers' first-round choice.

San Diego is exploring its options at outside linebacker in free agency. Dwight Freeney is scheduled to visit the team Wednesday. As of the early afternoon, he hadn't arrived yet.